Cathode ray tube



Dec. 12, 1939. F. W.-HEHLGANS I 2,183,398

' I CATHODE RAY TU'BE Original Filed May 23, 1933 Patented Dec. 12, 1939 UNITED STATES PATENT OFFICE- CATHODE RAY TUBE Original application May 23, 1933, Serial No.

672,489. Divided and this application November 7, June 4, 1932 3 Claims.

The present invention relates to electron discharge tubes, more particularly to cathode ray tubes utilized for sound recording or sound picture work.

This application is a division of my application Serial No. 672,489, filed May 23, 1933, and entitled Cathode ray tubes, now Patent 2,075,717 issued Mar. 10, 1937.

The electron tube has several advantages over other known light controlling means such as are lamps, neon discharge lamps, or Kerr cells, when employed for sound recording purposes. Some of these advantages are that the control of an electron discharge tube is almost Wholly devoid of inertia and the amount of energy required to carry out the control is relatively small.

Insofar as sound recording is concerned, the electron tube has heretofore been employed only as a light controlling means, operating on the intensity principle, in which case a Wehnelt cylinder is used for controlling the intensity of the electron beam and of the light spot on the fluorescent screen.

An object of the present invention is to improve the focusing device utilized in tubes of this general character. The improvement contemplates the efficient translation of a beam of electrons which is normally of circular configuration, or substantially so, into an elongated rectangular shape, vor narrow strip, suitable for producing light images on a photographic film. In carrying out this object, I propose to change the shape of the usual type of focusing member ordinarily provided for this purpose into a member which has a substantially elongated crosssectional shape and positioned at right angles to the axis of the electron beam. When a focusing member of the improved type is utilized, the light spot no longer appears on the fluorescent screen as a circular spot of variable diameter but as a narrow strip of light whose length varies in accordance with the voltage applied to the member. The light intensity of this strip has been found to remain remarkably constant when its length is controlled in this manner. When a negative potential is applied to the improved focusing member, the light strip may be caused to vanish if the potential is sufficiently high. The definition of the strip of light is the sharper, the smaller the distance between the oppositely disposed faces of the improved member.

The invention will be better understood when reference is made to the drawing in which Fig. 1 illustrates diagrammatically a cathode ray tube 1936, Serial No. 109,712. In Germany provided with the improved focusing and control member. Fig. 2 is a perspective view of a modified form of the member.

In Fig. 1, numeral l designates a highly evacuated or gas-containing envelope which terminates at oneend in a press 2 and at the other end is coated on the interior with a fluorescent substance to constitute a screen 3. Within the envelope there is a filamentary cathode 4 and a disk-like anode 5 provided with a central aperture 6 for the passage of electrons on their way to the screen. As is Well known, positive potential (not shown) may be applied between the filament 4 and the anode 5 to give the electrons sufficient velocity in order to reach and to impact with the screen.

In accordance with the present invention, there is provided between the filament and the anode the improved combined focusing and control member which may take the form of two pairs of metal plates l0, ll arranged preferably at right angles to one another. These plates may be conveniently supported from the press 2 by rigid wires 8 and I2 which may also serve as leading-in conductors. The two plates I 0, ll may either be all electrically connected together or connected electrically in opposite pairs. It will be noted that the distance between the respective pairs of plates is unequal. The light strip is thus given an elongated configuration at the fluorescent screen. The sharpness of the light strip may be controlled by simply changing the potential on one or the other pair of plates, or by applying a separate potential to each pair of plates. In case the potentials applied to the respective pairs of plates are different, there is no necessity of having the distances between the respective pairs of plates unequal, as obviously, the linearity of the electron beam may be obtained electrically by the difference in the applied potentials. If desired, one of the pairs of plates may be utilized solely for control purposes whereas the other pair may be used solely for elongating the normally round spot of light into the desired linear shape.

As shown in Fig. 2, instead of utilizing physically separate plates, electrically connected together, the improved focusing member 9 may be made of one piece having an elliptical configuration or that of a flattened cylinder. In this case, a lead-in wire may be taken from the member through the stem as in the case of Fig. 1. It is evident that in positioning the member 9 within the tube, the greater length of the opening in the member should be in the same direction as the direction which it is desired that the linear light strip shall take. Thus the electron beam appears on the fluorescent screen as a strip of light extending in the direction of the major axis of the member.

What I claim as new and desire to secure by Letters Patent of the United States, is:

1. A cathode ray tube containing a source of electrons, an anode, a fluorescent screen, and an electrostatic control member interposed between said source and anode for constraining the electrons to a flat rectangular shape whereby a strip of light is produced on said screen, said control member comprising two separate pairs of plates disposed at right angles to one another, each pair of oppositely disposed plates electrically connected together by an equipotential conductor.

2. In a cathode ray tube, a fluorescent screen, means including a cathode and an anode for producing a stream of electrons and allowing a substantial proportion of said stream to impinge on said screen so as to produce thereon a luminescent spot, and means for controlling the shape of said spot, said last-named means including means for applying two difierent and adjustable electric forces to the electron stream at substantially the same point along its axis, said forces being applied transversely to the stream in mutually perpendicular directions, and both acting symmetrically on .the stream to produce distortion thereof without simultaneously causing displacement of the axis of the stream.

3. In a cathode ray tube, a fluorescent screen, means including a cathode and an anode for producing a stream of electrons and allowing a substantial proportion of said stream to impinge on said screen so as to produce thereon a luminescent spot, and means positioned between said screen and cathode for controlling the shape of said spot, said last-named means comprising two electrically separate pairs of plates disposed at right angles to one another, the members of each pair of plates being oppositely disposed and being joined by a conductive connection so as to be maintained in substantially equipotential condition.

FRIEDRICH W. HEI-EGANS. 

